#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
    int h;
    int m;
    int num1;
    int num2;
    scanf("%d%d", &num1, &num2);
    h = num2 / 100 - num1 / 100;
    m = num2 % 100 - num1 % 100;
    if (m < 0)
    {
        m = 60 + m;
        h = h - 1;
    }
    printf("%02d:%02d\n", h, m);
    return 0;
}
